Precautions and Contraindications
Serious adverse reactions including nephrotoxicity and neurotoxicity have occurred in patients receiving systemic polymyxin B therapy. If polymyxin B is administered topically in conjunction with systemic polymyxin B therapy, the possibility of cumulative toxicity should be considered.
If itching, burning, inflammation, or other signs of sensitivity to polymyxin B occur, the drug should be discontinued.
Topical corticosteroids, when used in combination with topical polymyxin B, may mask the clinical signs of bacterial, fungal, or viral infections, or may suppress hypersensitivity reactions to the antibiotic or other ingredients in the formulations. The possibility of corticosteroid-induced adverse ocular effects, including increased intraocular pressure, glaucoma, papilledema, pseudotumor cerebri, ptosis, scleral malacia, and cataract formation, must also be considered.
The use of polymyxin B may result in overgrowth of nonsusceptible organisms, including fungi. If superinfection occurs, the drug should be discontinued and appropriate therapy instituted. Although some ophthalmic ointment vehicles used in the past were reported to retard corneal wound healing, currently used ophthalmic ointment vehicles do not appear to slow the rate of corneal wound healing; in addition, ointments may provide a protective effect if the cornea is exposed. However, the manufacturers caution that ophthalmic ointments have retarded corneal healing.
Some commercially available otic formulations of polymyxin B sulfate contain potassium metabisulfite, a sulfite that can cause allergic-type reactions, including anaphylaxis and life-threatening or less severe asthmatic episodes, in certain susceptible individuals. The overall prevalence of sulfite sensitivity in the general population is unknown but probably low; such sensitivity appears to occur more frequently in asthmatic than in nonasthmatic individuals.
Polymyxin B sulfate is contraindicated in patients with a history of hypersensitivity to any of the polymyxins or to any of the ingredients in the formulation.